Diastereoselective Synthesis of Biheterocyclic Tetrahydrothiophene

Jun 2, 2015 - reported by S. Vivek Kumar et al.,5 J.-J. Liang et al.,6 and S.-W. Duanet al.,7 and diversely spiro heterocyclic tetrahydrothio- phene d...
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Diastereoselective Synthesis of Biheterocyclic Tetrahydrothiophene Derivatives via Base-Catalyzed Cascade Michael-Aldol [3 + 2] Annulation of 1,4-Dithiane-2,5-diol with Maleimides Yuan Zhong,†,‡,§ Shixiong Ma,‡,§ Bai Li,† Xianxing Jiang,*,† and Rui Wang*,†,‡ †

School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, China School of Life Sciences, Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China

‡

S Supporting Information *

ABSTRACT: A highly diastereoselective intermolecular [3 + 2] annulation of 1,4-dithiane-2,5-diol to maleimides has been developed by using DABCO as a catalyst, which provides a series of highly functionalized biheterocyclic tetrahydrothiophene derivatives containing tetrahydrothiophene and pyrolidine backbones in excellent yields and diastereoselectivities (up to 98% yield and >20:1 d.r.). The cascade Michael-aldol reaction is capable of tolerating organic solvents as well as water.

T

DABCO-catalyzed [3 + 2] annulation of 1,4-dithiane-2,5-diol with maleimides to afford highly functionalized bicyclic compounds containing tetrahydrothiophene and pyrolidine backbones under mild reaction conditions with high efficiency. We initiated our studies by evaluating the reaction between 1,4-dithiane-2,5-diol 1 and N-benzyl maleimide 2a by basecatalysts in dichloromethane at room temperature. We found that this reaction proceeded quickly with 10 mol % Et3N and afforded the respective annulation products in 59% isolated yield and more than 20:1 diastereoselectivity within 40 min (Table 1, entry 1). Although high yields (up to 70% and 77%) were attained with the catalysts DBU and DIPEA, the diastereoselectivities were consistently poor (19:1 and 16:1) within 60 min (Table 1, entries 2 and 3). DABCO was found to be the most suitable catalyst for this reaction (Table 1, entry 4). Gratifyingly, a great improvement was observed by changing solvents, and the best yield (97%) and diastereoselectivity (>20:1) were obtained for product 3a when CHCl3 was used as a solvent (Table 1, entries 6−14). Surprisingly and remarkably, this reaction could also be performed in water with good yield (62%) and excellent diastereoselectivities (>20:1) within 30 min (Table 1, entry 15). In addition, when the catalyst loading was reduced to 5 or 1 mol %, respectively, no significant change in diastereoselectivities (>20:1) but poor yields (66%) were obtained (Table 1, entries 16 and 17). Next, the substrate scope of the reaction under the optimized conditions was summarized in Table 2. In general, all the reactions proceeded well to complete in less than 30 min to give the corresponding products in high yields and diaster-

hiophene derivatives are privileged structural units that are frequently encountered in many biologically active natural and synthetic compounds1 as well as in materials.2 In particular, some tetrahydrothiophene derivative backbones have attracted a great deal of attention, as they contain two biological, pharmaceutical, and agrochemical characteristics of both sulfur-containing compounds and biheterocycles (Figure 1).3 Therefore, the development of highly efficient synthetic methods to access these biheterocyclic compounds is particularly appealing. Commercially available 1,4-dithiane-2,5-diol (the dimer of mercaptoacetaldehyde) has been employed as an efficient substrate for the construction of tetrahydrothiophene derivatives via catalytic [3 + 2] annulation strategies.4 Recently, 1,4dithiane-2,5-diol has proved to be an attractive synthon for synthesizing a spiro heterocyclic compound and several methods for the synthesis of this structural unit have been reported by S. Vivek Kumar et al.,5 J.-J. Liang et al.,6 and S.-W. Duanet al.,7 and diversely spiro heterocyclic tetrahydrothiophene derivatives can be simply synthesized in good yields and diastereomeric ratio values. However, compared to the catalytic formation of spiroheterocycles, the biheterocyclic tetrahydrothiophenes have been much less studied. Furthermore, the reaction of 1,4-dithiane2,5-diol with maleimides has not yet been established, and we believe this represents a considerable challenge. However, the development of efficient methodologies that enable cheaper, simpler, and more concise approaches to access molecular complexity with exquisite levels of stereocontrol remains a preeminent goal in modern organic chemistry. Herein, we introduce a base-catalyzed strategy as a new and convenient platform for the design of intermolecular [3 + 2] annulation processes. In this context, we report an unprecedented © XXXX American Chemical Society

Received: April 22, 2015

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DOI: 10.1021/acs.joc.5b00897 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry

Figure 1. Structures of bioactive bicyclic tetrahydrothiophenes.

Table 1. Optimization of the Reaction Conditionsa

entry

cat.

x (mol %)

solvent

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Et3N DBU DIPEA DABCO Na2CO3 DABCO DABCO DABCO DABCO DABCO DABCO DABCO DABCO DABCO DABCO DABCO DABCO

10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 5 1

CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CHCl3 THF PhMe MTBE MeOH EtOAc Cl(CH2)2Cl acetone CH3CN H2O CHCl3 CHCl3

time (min)

yield (%)b

40 60 60 30

59 70 77 79 0 97 76 54 37 32 86 53 35 44 62 66 66

30 30 30 30 30 30 30 30 30 30 120 180

Table 2. Scope of N-Substituted Maleimidesa

d.r.c >20:1 19:1 16:1 >20:1 >20:1 14:1 17:1 15:1 4:1 16:1 17:1 4:1 4:1 >20:1 >20:1 >20:1

entry

R (2)

product (3)

yieldb

d.r.c

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Ph (2a) 4-MePh (2b) 4-MeOPh (2c) 4-FPh (2d) 4-ClPh (2e) 4-BrPh (2f) 4-NO2Ph (2g) 3-ClPh (2h) 2-ClPh (2i) 1-Naphthyl (2j) H (2k) Boc (2l) Me (2m) Et (2n) Bn (2o) Hex (2p)

3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k 3l 3m 3n 3o 3p

97 55 62 98 98 92 89 97 20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1

61 72 96 96 67

>20:1 4:1 >20:1 >20:1 >20:1

17:1

a

Reaction conditions: unless specified, a mixture of 1 (0.24 mmol), 2 (0.4 mmol), and DABCO (0.024 mmol) in CHCl3 (1.5 mL) was stirred for 30 min at rt. bIsolated yields. cDetermined by 1H NMR, and the configuration was assigned by comparison of X-ray crystal data of 3m, 5a, and 5b.

a Reaction conditions: unless specified, a mixture of 1 (0.24 mmol), 2a (0.4 mmol), and a catalyst (x mol %) in a solvent (1.5 mL) was stirred at rt. bIsolated yields. cDetermined by 1H NMR, and the configuration was assigned by comparison of X-ray crystal data of 3m, 5a, and 5b.

We also explored to remove the Boc group of product 3l. Under the acidic condition, the reaction gave the Nunprotected product 3k in high yield. Moreover, the NH of the unprotected compound 3k can be easily further modified (Scheme 1). We further extended the scope of the reaction, and 1,3diphenylmaleimide proved to be amenable to this catalytic method, which gave the respective annulation products with

eoselecttivities. Nonsubstituted or electron-withdrawing substituents at the para- or meta-position on the aromatic ring as well as 1-naphthyl in maleimide diversifications were tolerated, affording the desired products in excellent yields and diastereoselectivities (Table 2, entries 1, 4−8 and 10). The substrates with electron-donating substituents at para-position afforded the diastereoselectivities at the same levels albeit with moderate yields. (Table 2, entries 2 and 3). However, the substrates with ortho-substituent on aryl ring led to almost no product (Table 2, entries 9). Maleimide 2l bearing an N-Boc group also proceeded with low yield, while when employing maleimide 2k without protecting groups, no reaction occurred (Table 2, entries 11−12). It is noteworthy that the reactions of aliphatic-substituted maleimides 2n and 2o could proceed smoothly under standard conditions, giving the desired products in 96% yields with >20:1 d.r., whereas the yield was remarkably decreased for 2m and 2p (Table 2, entries 13−16). The absolute configuration of the products obtained through the Michael-aldol cascade process was determined by an X-ray analysis of compound 3m8 (see Supporting Information).

Scheme 1. Removal of the Boc Group in Compound 3l

B

DOI: 10.1021/acs.joc.5b00897 J. Org. Chem. XXXX, XXX, XXX−XXX

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good yields. The absolute configuration of biheterocyclic tetrahydrothiophene derivatives were unambiguously confirmed by the X-ray crystallographic analysis, as shown in Supporting Information, and it is composed of (C8R, C9R, and C11R) configuration for 5a and (C8R, C9R, and C11S) configuration for 5b9 (Scheme 2).

Note

EXPERIMENTAL SECTION

General Methods. Unless stated otherwise, all reactions were carried out in flame-dried glassware. All solvents were purified and dried according to standard methods prior to use. Reactions were monitored by thin layer chromatography (TLC), and column chromatography purifications were carried out using silica gel. 1H, 13 C, and 19F NMR spectra were recorded using (CD3)2SO, (CD3)2CO, or CDCl3 assolvents and TMS as an internal standard. The peak patterns of 1H NMR are indicated as follows: s, singlet; d, doublet; t, triplet; dd, doublet of doublet; and m, multiplet. The coupling constants, J, are reported in hertz (Hz). Data for 19F NMR and 13C NMR are reported in terms of chemical shift and multiplicity. HRMS were performed on a Q-tof mass instrument (ESI). 1,4Dithiane-2,5-diol 1, all reagents, and catalysts were obtained from commercial sources and were used without further purification. All reactions were conducted in a closed system and were monitored by TLC. N-Substituted maleimides 210 and 1,3-diphenylmaleimide 411 were prepared according to the literature method or a similar method. General Procedure for the Synthesis of 3a−3h, 3j−3p, 5a, and 5b. An ordinary vial equipped with a magnetic stirring bar was charged with 1,4-dithiane-2,5-diol 1 (0.24 mmol) and maleimides 2 (0.4 mmol) in CHCl3 (1.5 mL), and then DABCO (4.5 mg, 10 mol %) was added. The stirring was maintained at room temperature for 30 min. The reaction mixture was directly charged onto silica gel and purified through flash chromatography (CH2Cl2/EtOAc = 4:1) to furnish the corresponding products 3. (3S,3aS,6aS)-3-Hydroxy-5-phenyldihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3a). Yield 97% (97 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.51- 7.39 (m, 3H), 7.22 (d, J = 7.2 Hz, 2H), 5.66 (d, J = 3.9 Hz, 1H), 4.78 (s, 1H), 4.60 (d, J = 8.7 Hz, 1H), 3.65 (dd, J = 8.9, 5.3 Hz, 1H), 3.21 (dd, J = 11.6, 2.9 Hz, 1H), 2.93 (dd, J = 11.7, 1.8 Hz, 1H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 176.14, 173.68, 132.92, 129.36, 128.80, 127.47, 74.65, 55.34, 48.62, 42.94. ESI-HRMS: calcd. for C12H11NO3S + H+ 250.0532; found, 250.0538. (3S,3aS,6aS)-3-Hydroxy-5-(p-tolyl)dihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3b). Yield 55% (58 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.25 (d, J = 8.1 Hz, 2H), 7.14 (d, J = 8.3 Hz, 2H), 4.78−4.69 (m, 1H), 4.19 (d, J = 8.3 Hz, 1H), 3.84 (d, J = 7.5 Hz, 1H), 3.53 (dd, J = 8.2, 6.5 Hz, 1H), 3.11 (dd, J = 11.7, 4.4 Hz, 1H), 2.83 (dd, J = 11.8, 6.6 Hz, 1H), 2.37 (s, 3H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 175.5, 175.1, 139.2, 129.9, 128.7, 126.3, 76.0, 51.1, 45.4, 39.2, 21.3. ESI-HRMS: calcd. for C13H13NO3S + H+ 264.0689; found, 264.0691. (3S,3aS,6aS)-3-Hydroxy-5-(4-methoxyphenyl)dihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3c). Yield 62% (69 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2CO): δ (ppm) 7.20 (d, J = 8.9 Hz, 2H), 7.00 (d, J = 8.9 Hz, 2H), 4.94−4.92 (m, 1H), 4.66 (s, 1H), 4.53 (d, J = 8.9 Hz, 1H), 3.82 (s, 3H), 3.72 (dd, J = 8.9, 5.6 Hz, 1H), 3.29 (dd, J = 11.7, 3.4 Hz, 1H), 3.00 (dd, J = 11.7, 3.4 Hz, 1H). 13 C NMR (75 MHz, (CD3)2CO): δ (ppm) 176.4, 174.4, 160.3, 129.1, 126.4, 114.8, 76.1, 55.8, 55.0, 48.5, 42.5. ESI-HRMS: calcd. for C13H13NO4S + Na+ 302.0457; found, 302.0465. (3S,3aS,6aS)-5-(4-Fluorophenyl)-3-hydroxydihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3d). Yield 98% (105 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.36− 7.24 (m, 4H), 5.69 (d, J = 4.0 Hz, 1H), 4.78 (s, 1H), 4.58 (d, J = 8.9 Hz, 1H), 3.66 (dd, J = 8.9, 5.2 Hz, 1H), 3.21 (dd, J = 11.6, 2.9 Hz, 1H), 2.93 (dd, J = 11.6, 2.1 Hz, 1H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 176.1, 173.7, 161.9 (JC−F = 243.8HZ), 129.6 (JC−F = 9HZ), 129.1 (JC−F = 3HZ), 116.3 (JC−F = 22.5HZ), 74.7, 55.3, 48.6, 42.9. 19F NMR (282 MHz, (CD3)2SO) δ (ppm) −112.97. ESI-HRMS: calcd. for C12H10FNO3S + Na+ 290.0258; found, 290.0261. (3S,3aS,6aS)-5-(4-Chlorophenyl)-3-hydroxydihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3e). Yield 98% (111 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.63 (d, J = 8.6 Hz, 2H), 7.32 (d, J = 8.6 Hz, 2H), 5.74 (d, J = 3.0 Hz, 1H), 4.83 (s, 1H), 4.65 (d, J = 8.9 Hz, 1H), 3.72 (dd, J = 8.9, 5.2 Hz, 1H), 3.27 (dd, J = 11.6, 2.8 Hz, 1H), 2.98 (dd, J = 11.6, 1.9 Hz, 1H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 175.5, 173.0, 132.8, 131.2, 129.0,

Scheme 2. Synthesis of 3-Hydroxy-3a,5-diphenyldihydro-2Hthieno[2,3-c]pyrrole-4,6(5H,6aH)-dione

On the basis of the experimental results described above, a plausible catalytic cycle of the current cascade reaction is outlined in Scheme 3. The mercaptoacetaldehyde that is Scheme 3. Proposed Mechanism of the Michael-Aldol Reaction

generated from 1,4-dithiane-2,5-diol under equilibrium conditions could be activated by the tertiary amine of DABCO to form intermediate B. It undergoes the intermolecular sulfaMichael addition to provide intermediate A. Subsequent intramolecular aldol reaction through nucleophilic attack of in situ enolate to the aldehyde moiety in excellent diastereoselective fashion, then followed by the regeneration of the DABCO provides the biheterocyclic tetrahydrothiophene compounds. The absolute configuration of the major product was determined as (C8R, C9R, and C11R) by using the X-ray crystallographic analysis of 5a. In summary, We have disclosed an unprecedented DABCOcatalyzed [3 + 2] Michael-aldol annulation of 1,4-dithiane-2,5diol with maleimides to afford highly functionalized bicyclic compounds containing tetrahydrothiophene and pyrolidine backbones with high efficiency. The construction proceeds under mild conditions, providing a range of compounds in excellent yields and diastereoselectivities (up to 98% yield and >20:1 d.r.). In particular, the procedure is capable of tolerating a relatively wide range of solvents, especially in water. We consider that the utility of biheterocyclic tetrahydrothiophene derivatives may exhibit promising applications in drug discovery or chemical biology. The biological evaluation of these products is currently underway by our group. C

DOI: 10.1021/acs.joc.5b00897 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry

(3S,3aS,6aS)-5-Benzyl-3-hydroxydihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3o). Yield 96% (101 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2CO): δ (ppm) 7.21−7.09 (m, 5H), 4.68 (dd, J = 8.8, 4.3 Hz, 1H), 4.47 (d, J = 7.8 Hz, 2H), 4.41 (d, J = 4.2 Hz, 1H), 4.24 (d, J = 8.7 Hz, 1H), 3.50 (dd, J = 8.7, 5.9 Hz, 1H), 3.05 (dd, J = 11.7, 3.6 Hz, 1H), 2.72 (dd, J = 11.7, 4.2 Hz, 1H). 13C NMR (75 MHz, (CD3)2CO): δ (ppm) 177.0, 175.1, 137.2, 129.3, 128.7, 128.3, 75.8, 54.5, 48.1, 42.8, 42.2. ESI-HRMS: calcd. for C13H13NO3S + H+ 264.0689; found, 264.0695. (3S,3aS,6aS)-5-Cyclohexyl-3-hydroxydihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3p). Yield 67% (68 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2CO): δ (ppm) 4.82−4.76 (m, 1H), 4.45 (d, J = 5.6 Hz, 1H), 4.28 (d, J = 8.7 Hz, 1H), 3.3.93−3.82 (m,1H), 3.53 (dd, J = 8.7, 5.9 Hz, 1H), 3.22−3.17 (m, 1H), 2.85 (dd, J = 11.6, 4.4 Hz, 1H), 2.16−2.03 (m, 2H), 1.81−1.77 (m, 2H), 1.66− 1.55 (m, 3H), 1.38−1.21 (m, 3H). 13C NMR (75 MHz, (CD3)2CO): δ (ppm) 177.0, 175.3, 76.0, 53.6, 52.3, 47.7, 41.5, 29.6, 29.4, 26.5, 26.0. ESI-HRMS: calcd. for C12H17NO3S + H+ 256.1002; found, 256.1005. (3R,3aR,6aR)-3-Hydroxy-3a,5-diphenyldihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (5a). Yield 42% (55 mg); brown solid. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.77 (d, J = 7.5 Hz, 2H), 7.52−7.36 (m, 6H), 7.28 (d, J = 7.3 Hz, 2H), 6.31 (d, J = 2.3 Hz, 1H), 5.13 (s, 1H), 4.76 (s, 1H), 2.91 (s, 2H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 174.9, 174.4, 135.7, 133.1, 129.4, 129.0, 129.0, 128.5, 127.7, 127.5, 82.4, 68.0, 52.4. ESI-HRMS: calcd. for C18H15NO3S + H+ 326.0845; found, 326.0849. (3S,3aR,6aR)-3-Hydroxy-3a,5-diphenyldihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (5b). Yield 23% (30 mg); brown solid. 1H NMR (300 MHz, CDCl3): δ (ppm) 7.60−7.56 (m, 2H), 7.48−7.37 (m, 6H), 7.25−7.20 (m, 2H), 5.20 (s, 1H), 4.60 (s, 1H), 3.33 (dd, J = 12.8, 3.2 Hz, 1H), 3.14 (dd, J = 12.8, 1.4 Hz, 1H), 1.17 (d, J = 6.3 Hz, 1H). 13C NMR (75 MHz, CDCl3): δ (ppm) 175.7, 174.8, 133.0, 131.3, 129.4, 129.3, 129.0, 127.5, 126.5, 126.2, 79.0, 69.4, 50.3, 39.4. ESI-HRMS: calcd. for C18H15NO3S + H+ 326.0845; found, 326.0848.

128.7, 74.2, 54.2, 54.9, 48.1, 42.4. ESI-HRMS: calcd. for C12H11ClNO3S + H+ 284.0143; found, 284.0152. (3S,3aS,6aS)-5-(4-Bromophenyl)-3-hydroxydihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3f). Yield 92% (120 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.70 (d, J = 8.7 Hz, 2H), 7.19 (d, J = 8.7 Hz, 2H), 5.68 (d, J = 3.9 Hz, 1H), 4.79−4.75 (m, 1H), 4.58 (d, J = 8.9 Hz, 1H), 3.66 (dd, J = 8.9, 5.1 Hz, 1H), 3.21 (dd, J = 11.6, 3.0 Hz, 1H), 2.92 (dd, J = 11.6, 2.2 Hz, 1H). 13 C NMR (75 MHz, (CD3)2SO): δ (ppm) 175.9, 173.5, 132.4, 132.1, 129.5, 121.8, 74.7, 55.4, 48.6, 42.9. ESI-HRMS: calcd. for C12H11BrNO3S + H+ 327.9638; found, 327.9641. (3S,3aS,6aS)-3-Hydroxy-5-(4-nitrophenyl)dihydro-2H-thieno[2,3c]pyrrole-4,6(5H,6aH)-dione (3g). Yield 89% (105 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 8.37 (d, J = 8.9 Hz, 2H), 7.56 (d, J = 8.9 Hz, 2H), 5.74 (d, J = 2.9 Hz, 1H), 4.80 (s, 1H), 4.63 (d, J = 9.0 Hz, 1H), 3.71 (dd, J = 8.9, 5.2 Hz, 1H), 3.23 (dd, J = 11.6, 2.8 Hz, 1H), 2.94 (dd, J = 11.6, 1.9 Hz, 1H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 175.7, 173.2, 147.0, 138.3, 128.2, 124.8, 74.8, 55.5, 48.7, 43.0. ESI-HRMS: calcd. for C12H10N2O5S + Na+ 317.0203; found, 317.0202. (3S,3aS,6aS)-5-(3-Chlorophenyl)-3-hydroxydihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3h). Yield 97% (110 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.44− 7.39 (m, 2H), 7.36- 7.35 (m, 1H), 7.26−7.22 (m, 1H), 4.88−4.79 (m,1H), 4.27 (d, J = 8.2 Hz, 1H), 3.66 (dd, J = 8.1, 6.6 Hz, 1H), 3.51 (d, J = 8.8 Hz, 1H), 3.23 (dd, J = 11.8, 4.7 Hz, 1H), 2.91 (dd, J = 11.8, 7.5 Hz, 1H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 174.6, 134.8, 132.2, 130.3, 129.3, 126.6, 124.6, 76.2, 50.7, 44.9, 38.8. ESI-HRMS: calcd. for C12H10ClNO3S + Na+ 305.9962; found, 305.9972. (3S,3aS,6aS)-3-Hydroxy-5-(naphthalen-1-yl)dihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3j). Yield 97% (116 mg); white solid; d.r. = 17:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 8.08− 7.86 (m, 3H), 7.65−7.29 (m, 4H), 6.04−5.80 (m, 1H), 4.92−4.71 (m, 2H),3.83−3.77 (m, 1H), 3.34−3.26 (m, 1H), 3.02 (t, J = 11.0 Hz, 1H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 176.7, 173.9, 134.1, 130.2, 130.1, 129.8, 128.5, 127.2, 127.1, 127.0, 126.0, 123.8, 74.1, 56.2, 49.2, 43.7. ESI-HRMS: calcd. for C16H13 NO3S + H+ 300.0689; found, 300.0695. (3S,3aS,6aS)-3-Hydroxydihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3k). Yield 82% (60 mg); yellow solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 7.66 (s, 1H), 7.33 (s, 1H), 5.30 (s, 1H), 3.92 (s, 1H), 3.27 (dd, J = 11.2, 1.9 Hz, 1H), 3.08 (dd, J = 8.4, 2.7 Hz, 2H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 173.1, 169.5, 81.9, 57.6, 43.9, 37.0. ESI-HRMS: calcd. for C6H7NO3S + Na+ 196.0039; found, 196.0043. (3S,3aS,6aS)-tert-Butyl 3-hydroxy-4,6-dioxotetrahydro-2Hthieno[2,3-c]pyrrole-5(3H)-carboxylate (3l). Yield 61% (67 mg); white solid; d.r. > 20:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 8.20 (s, 1H), 5.26 (s, 1H), 3.76 (d, J = 5.9 Hz, 2H), 3.42−3.37 (m, 1H), 3.17 (d, J = 11.0 Hz, 1H), 1.43 (s, 9H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 172.1, 169.8, 150.8, 83.8, 80.5, 58.4, 43.9, 36.9, 27.9. ESI-HRMS: calcd. for C11H15NO5S + Na+ 296.0563; found, 296.0564. (3S,3aS,6aS)-3-Hydroxy-5-methyldihydro-2H-thieno[2,3-c]pyrrole-4,6(5H,6aH)-dione (3m). Yield 72% (54 mg); white solid; d.r. = 4:1. 1H NMR (300 MHz, (CD3)2SO): δ (ppm) 4.74−4.66 (m, 1H), 4.11 (d, J = 8.2 Hz, 1H), 3.90 (d, J = 7.5 Hz, 1H), 3.51−3.46 (m, 1H), 3.09 (dd, J = 11.7, 4.5 Hz, 1H), 2.95 (s, 3H), 2.75 (dd, J = 11.7, 7.0 Hz, 1H). 13C NMR (75 MHz, (CD3)2SO): δ (ppm) 176.5, 175.8, 75.6, 50.8, 45.3, 38.9, 25.2. ESI-HRMS: calcd. for C7H9NO3S + Na+ 210.0195; found, 210.0196. (3S,3aS,6aS)-5-Ethyl-3-hydroxydihydro-2H-thieno[2,3-c]pyrrole4,6(5H,6aH)-dione (3n). Yield 96% (77 mg); white solid; d.r. > 20:1. 1 H NMR (300 MHz, (CD3)2CO): δ (ppm) 4.85−4.78 (m, 1H), 4.47 (d, J = 5.3 Hz, 1H), 4.35 (d, J = 8.7 Hz, 1H), 3.61 (dd, J = 8.7, 5.9 Hz, 1H), 3.46 (dt, J = 14.1, 6.9 Hz, 2H), 3.22 (dd, J = 11.7, 3.6 Hz, 1H), 2.88 (dd, J = 11.7, 4.2 Hz, 1H), 1.09 (t, J = 7.2 Hz, 3H). 13C NMR (75 MHz, (CD3)2CO): δ (ppm) 176.8, 175.0, 75.8, 54.2, 48.0, 41.9, 34.2, 13.1. ESI-HRMS: calcd. for C8H11NO3S + H+ 202.0532; found, 202.0535.

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ASSOCIATED CONTENT

S Supporting Information *

X-ray crystallographic data for 3m, 5a, and 5b (CIF), and 1H, 13 C, and 19F NMR spectra. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.5b00897.

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AUTHOR INFORMATION

Corresponding Authors

*(X.J.) E-mail: [email protected]. *(R.W.) E-mail: [email protected]. Author Contributions §

Y.Z. and S.M. contributed equally to this work.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are grateful for the grants from the Start-up Grant from Sun Yat-sen University (No. 36000-31121300), the NSFC (Nos. 91213303, 21102141, 21272107, and 21202072), and Major Scientific and Technological Project of Guangdong Province (No. 2011A080300001).

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REFERENCES

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DOI: 10.1021/acs.joc.5b00897 J. Org. Chem. XXXX, XXX, XXX−XXX

Note

The Journal of Organic Chemistry 1997. (b) Pelter, A.; Jenkins, I.; Jones, D. E. Tetrahedron 1997, 53, 10357. (c) Handbook of Oligo- and Polythiophenes; Fichou, D., Ed.; Wiley-VCH: Weinheim, Germany, 1999. (d) Muccini, M. Nat. Mater. 2006, 5, 605. (3) For selected examples on the synthesis of thiophene derivatives, see: (a) Johnson, J. W.; Evanoff, D. P.; Savard, M. E.; Lange, G.; Ramadhar, T. R.; Assoud, A.; Taylor, N. J.; Dmitrienko, G. I. J. Org. Chem. 2008, 73, 6970. (b) Benetti, S.; De Risi, C.; Pollini, G. P.; Zanirato, V. Chem. Rev. 2012, 112, 2129. (4) For selected examples, see: (a) Ling, J.-B.; Su, Y.; Zhu, H.-L.; Wang, G.-Y.; Xu, P.-F. Org. Lett. 2012, 14, 1090. (b) Su, Y.; Ling, J.-B.; Zhang, S.; Xu, P.-F. J. Org. Chem. 2013, 78, 11053. (5) Vivek Kumar, S.; Prasanna, P.; Perumal, S. Tetrahedron Lett. 2013, 54, 6651. (6) Liang, J.-J.; Pan, J.-Y.; Xu, D.-C.; Xie, J.-W. Tetrahedron Lett. 2014, 55, 6335. (7) Duan, S.-W.; Li, Y.; Liu, Y.-Y.; Zou, Y.-Q.; Shi, D.-Q.; Xiao, W.-J. Chem. Commun. 2012, 48, 5160. (8) CCDC 1031892 3m contains the supplementary crystallographic data for this note. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/ data_request/cif. (9) CCDC 1400568 5a and CCDC 1053203 5b contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. (10) Cava, M. P.; Deana, A. A.; Muth, K.; Mitchell, M. J. Org. Synth. 1961, 41, 93. (11) Matuszak, N.; Muccioli, G. G.; Labar, G.; Lambert, D. M. J. Med. Chem. 2009, 52, 7410.

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DOI: 10.1021/acs.joc.5b00897 J. Org. Chem. XXXX, XXX, XXX−XXX